1. Field of the Invention
The present invention relates to a vehicle drive apparatus including an electric motor.
2. Description of Related Art
In a vehicle drive apparatus that includes an electric motor, a system for supplying oil that is thrown up by a specified gear in the drive apparatus to a gear and a bearing and for supplying the pumped-up oil by an oil pump to the an electric motor has been adopted for a mechanism that lubricates the gear and the bearing and cools the electric motor, the oil pump being disposed along with the gear. There is a case where an oil amount supplied to the gear and the bearing is changed by an oil temperature, and thus it may be difficult to constantly and sufficiently secure a required oil amount. For example, when the oil temperature is low, viscosity of the oil is high. Thus, the oil amount that is supplied to the bearing for a purpose of lubrication may be reduced. On the other hand, when the oil temperature is high, the viscosity of the oil is low. Consequently, a larger oil amount than the required oil amount is thrown up and supplied to the gear and the bearing. Thus, agitation loss of the oil may be increased.
On the contrary to the above, Japanese Patent Application Publication No. 2011-152814 (JP 2011-152814 A) discloses a hybrid vehicle drive apparatus that includes a motor chamber and a gear chamber that are formed with a partitioning wall being formed therebetween. The motor chamber houses an electric motor within a case, and the gear chamber houses various types of gears. Oil reserved in a lower section of the gear chamber is pumped up by an oil pump and supplied to a feed pump for supplying the oil to the gear chamber and the motor chamber. This feed pump is provided with a thermostat that can block a flow of the lubrication oil from the gear chamber side to the motor chamber side. Furthermore, a communicating section of the partitioning wall communicates between the motor chamber and the gear chamber and is provided with a solenoid valve, an opened/closed state of which is controlled in accordance with an oil temperature detected by an oil temperature sensor. In the vehicle drive apparatus that is configured as above, the opened/closed state of the solenoid valve is controlled in accordance with the oil temperature detected by the oil temperature sensor, and distribution of the oil to the motor chamber and the gear chamber is adjusted to be optimal. For example, the thermostat blocks the oil supply to the motor chamber and closes the solenoid valve in an extremely low temperature condition. Accordingly, the oil supply to the motor chamber is stopped, and the oil is circulated within the gear chamber. In other words, an oil circulation area is reduced, so as to promptly increase the oil temperature. For example, once the oil is heated to a high temperature, the thermostat permits the oil supply to the motor chamber and thus opens the solenoid valve. Accordingly, the oil circulation area is expanded, so as to promptly lower the oil temperature.